1. 1 Hiding Data in Images by Simple LSB Substitution Source: Pattern Recognition, Vol. 37, pp. 469-474, 2004 Authors: Chi-Kwong Chan and L.M. Cheng Speaker: Chia-Chun Wu ( 吳佳駿 ) Date: 2004/12/23

2. 2 Outline Introduction Data hiding by simple LSB substitution Optimal pixel adjustment process Experimental results Conclusions Comments

3. 3 Introduction The least-significant-bit (LSB) planes Directly replacing the LSBs of the cover- image with the message bits. Typically achieve high capacity. Using the proposed algorithm, the worst mean-square-error (WMSE) between the cover-image and the stego-image is shown to be 1/2 of that obtained by the simple LSB substitution method.

4. 4 Data Hiding by Simple LSB Substitution Message bits: 100011101110 K=3 101 01100101 20 00010100 66 01000010 220 11011100 100 01100100 19 00010011 69 01000101 222 11011110 Cover-imageStego-image

5. 5 Worst PSNR by Simple LSB Substitution Worst PSNR for k = 1–5 by simple LSB substitution

6. 6 Optimal Pixel Adjustment Process (OPAP) Stego-pixelover-pixel P' 10011111 10101110 10101100 11000001 P 10011000 10101110 10101101 11000111 Error(δ) 7 0 -6

7. 7 Optimal Pixel Adjustment Process (Cont ’ ) Stego-pixel after OPAP Interval 1Interval 2Interval 3

8. 8 Optimal Pixel Adjustment Process (Cont ’ ) P' 10011111 10101110 10101100 11000001 P 10011000 10101110 10101101 11000111 Error(δ) 7 0 -6 P' 10011111 10101110 10101100 11000001 P" 10010111 10101110 10101100 11001001 -2 k +2 k

9. 9 Optimal Pixel Adjustment Process (Cont ’ ) 出現的機率非常小

10. 10 Optimal Pixel Adjustment Process (Cont ’ ) The percentage of cover image pixels associated with the five cases (Eq. (12)) when the reduced-sized images of Fig. 2 are embedded into the cover-images

11. 11 Optimal Pixel Adjustment Process (Cont ’ )

12. 12 Experimental Results (a) Simple LSB-substitution method; (b) proposed method (4-bit insertion).

13. 13 Experimental Results (Cont ’ ) The results of embedding the random messages into the first set of cover-images

14. 14 Experimental Results (Cont ’ ) The results of embedding the reduced-sized image of Fig. 2 into the first set of cover-images

15. 15 Experimental Results (Cont ’ ) The results of embedding the reduced-sized image of Fig. 2 into the second set of cover-images

16. 16 Conclusions Low computational complexity. Image quality improvement.

17. 17 Comments 此方法可以套用在浮水印的應用上